Many vehicles include passive entry systems that allow a user to enter and start the vehicle without a key, simply requiring the driver to carry a key fob. The systems are referred to as ‘passive’ because they do not require any action from the user. Conventional systems utilize a low frequency radio frequency identification (LF RFID) tag that provides short range communication, and an ultra-high frequency (UHF) transceiver for longer range communication. However, the security of such systems can possibly be circumvented through a “relay attack” that enables an attacker to open or even start the vehicle without the key fob.
In general, a “relay attack” extends the range of the radio frequency transmitter (the key fob) and intercepts the data being transmitted between the key fob and the vehicle. During the relay attack, the LF signal from the vehicle is relayed over a purpose-built RF link composed of an emitter and receiver. The emitter captures the LF signal and up-converts it to higher frequency, which is then amplified and transmitted over the air. The receiver receives the signal and down-converts it to obtain the original LF signal. The LF signal is then amplified again and sent to a loop LF antenna, which reproduces the signal that the vehicle emitted. The attacker can then present the relaying antenna in front of the door handle for the key fob to send the open signal, and then bring the antenna inside the vehicle to send a vehicle start message and start the vehicle. While current systems do work well for their intended purpose, there remains a need for improvement in the relevant art.